In Bluetooth®, a network is formed from a master which executes polling control to control the communication timing and access of a communication device and a slave which executes communication in accordance with a signal from the master. A piconet can be formed by one master and seven slaves at maximum.
In Bluetooth®, a scatternet which participates and communicates in a plurality of piconets is defined. For example, when a communication device connected to an access point (first piconet) wants to participate in another piconet (e.g., a second piconet to a communication device such as a PC), the communication mode to the master (the access point in this case) which controls the first piconet is temporarily changed to a power saving mode for intermittent reception. With this processing, connection to the access point is temporarily opened so that communication can be executed at the communication timing of the second piconet.
In the piconet operation of Bluetooth®, communication devices (slaves) communicate with each other through the master that controls access timing. For this reason, traffic in the radio section increases, and no efficient data transfer can be done. Even in the scatternet operation described in the prior art as a means for avoiding this problem, since a clock frequency shift occurs between masters, the initially set access time cannot be ensured. This is because the access timing to a specific slave device (to be referred to as a slave 1 hereinafter) is controlled in accordance with the timing of the power saving mode set with respect to a master which operates asynchronously.
When communication traffic to the slave 1 changes, and the communication time to one master is to be changed, the power saving mode shift time must be reset between the slave 1 and each master. It is therefore difficult to sequentially adapt the access time in accordance with a change in traffic. To solve this problem, a method has been examined in Bluetooth SIG, in which a slave which participates in a plurality of piconets is caused to notify each master of the time (communication hold time) of nonparticipation in the piconet. However, how to notify the master of the communication hold time is not disclosed. It is hard to perform access control according to the communication condition such as traffic.
As described above, in the communication scheme that allows one communication apparatus to belong to a plurality of networks simultaneously, the timing to permit the communication apparatus to access each network or the timing to inhibit access must be adjusted, though the adjustment is difficult.